Pump unloading device



United States Patent Ofifice 3,366,062 PUMP UNLOADING DEVICE James D. Kelsey, Corry, Pa., assignor to Cooper Industries, Inc., Mount Vernon, Ohio, a corporation of Ohio Filed Apr. 25, 1966, Ser. No. 545,008 4 Claims. (Cl. 10311) ABSTRACT OF THE DISCLOSURE A device for loading and unloading a reciprocating pump by holding open its intake or suction valves. To eliminate shock waves and undue stress on the pump parts, the device includes a synchronized timing control to assure that each valve is unloaded or loaded only during the suctionstroke of its associated piston. The device includes a fluid pressure operated unloading stem which, when in operative position, is effective to inter fere with the normal operation of the valve and to hold it in open position. The timing control includes a fluid valve member driven in synchronism with the pump crankshaft and having fluid passages positioned such that the fluid pressure operated unloading stem will be actuated or deactuated only during the suction stroke of its associated piston.

This invention relates to an apparatus for loading and unloading reciprocating pumps. More specifically, this device of this invention relates to a device to be used with reciprocating pumps, particularly of the multicylinder type, which is capable of loading or unloading the pump from zero to full capacity and vice versa without the necessity of stopping or otherwise altering the speed of the prime mover and without shock or undue strain on the moving parts of the pump.

In reciprocating pumps in commonly used water sup ply and hydraulic control systems, etc., it is often desirable to temporarily completely unload or reduce to zero the output of the pump. One way of doing this is, of course, to start and stop the prime mover of the pump, which may be an electric motor or internal combustion engine. In many instances, this method of operation is disadvantageous due to the fact that starting the pump against the full load of the system requires a higher torque motor and also, the short periods of unloading, it is undesirable to completely stop the prime mover.

A better method of pump loading and unloading can be accomplished by disabling or holding open the intake or suction valves in each of the pump cylinders so that, as the pistons in the cylinders continue to reciprocate, the liquid therein merely sloshes or is moved back and forth in the suction or intake manifold and no output pressure within the cylinders is produced. This method is commonly used to load or unload fluid compressors. For instance, United States Patent 2,865,557 discloses an apparatus for holding open the suction valve of a fluid compressor which may be manually actuated by the operator when it is desired to load or unload the compressor. United States Patent 2,673,025 discloses a constant speed, variable capacity compressor in which one or more cylinders may be loaded or unloaded by holding open the suction valve by means of a pressure differential controlled by the output pressure of the. compressor.

The diificulty in using this method of loading or unloading in a pumping system is because, unlike compressors which handle a compressible fluid medium, pumps for water or hydraulic fluids handle relatively incompressible liquids. In a multi-cylinder pump, the simultaneous loading or unloading of each cylinder by disabling or releasing the suction valve therein would create a shock 3,366,062 Patented Jan. 30, 1968 wave and undue stress on the pump and its prime mover. In addition, if any cylinder on a reciprocating pump is loaded, that is, if its suction valve is suddenly closed, during the discharge (pressure) stroke of the piston, a sudden shock pressure of damaging magnitude would result.

It has been discovered that reciprocating pumps may be quickly and efiiciently loaded and unloaded 'by disabling or releasing the suction valve of each cylinder thereof, as long as the disabling or release of a suction valve takes place during the suction (intake) stroke of the piston of that cylinder. By confining the unloading or loading of the pump cylinders to the suction or intake stroke of their pistons, the shock waves and pressures produced as previously described are avoided and in addition, in multi-cylinder installations a progressive sequence of loading or unloading of the cylinders is established in accordance with the predetermined suction or intake stroke sequence of the pump.

Accordingly, it is an object of this invention to provide an apparatus for loading and unloading reciprocating pumps, which apparatus is effective to disable or hold open the suction valve of each pump cylinder for unloading and to release these valves for loading, with the disable or release being performed only during the suction or intake strokes of the pump pistons.

It is another object of this invention to provide an apparatus for use with a multi-cylinder reciprocating pump capable of loading or unloading the entire pump by disabling or releasing the suction valves of the cylinders in a predetermined sequence corresponding to the predetermined sequence of the suction or intake strokes of the pistons, or in which the loading and unloading may be accomplished at full pump speed without damaging shock waves or pressure.

Other objects and advantages of the invention will be apparent to those skilled in the art from the following detailed description of a preferred embodiment thereof, reference being made to the accompanying drawings in which:

FIG. 1 is a schematic view of three cylinders of a multi-cylinder reciprocating pump and their common crankshaft, each cylinder having a pressure actuated intake (suction) valve and exhaust valve, and an unloader device associated with its intake valve;

FIG. 2 is a schematic view, partially in cross section, of a preferred pump unloading and loading device of this invention as it is associated with the suction valves of three cylinders of the multi-cylinder pump schematically shown in FIG. 1;

FIG. 3 is a view in elevation, taken along line 3- of FIG. 2 and showing on enlarged scale, a pneumatic timing control valve used to control the actuation of the pumploading and unloading device for each cylinder and;

FIG. 4 is a cross-sectional view taken along line 4-4 of FIG. 3 and showing the internal construction of the pneumatic control valve of FIG. 3.

It is to be understood that, in the following detailed description of the preferred embodiment with reference being made to the loading and unloading device as it is associated with three cylinders of a multi-cylinder reciprocating pump, the device may be used effectively with a single cylinder reciprocating pump and also may be used with single or multi-cylinder reciprocating compressors where it would be desirable to eliminate all or portions of the shock or pressure waves which might be produced by the simultaneous loading or unloading of each of the cylinders in the compressor, even though the compressor may be designed for handling fluids having a substantial degree of compressibility.

Referring to FIGURE 1, each of the cylinders A, B, and C of the reciprocating pump has an associated intake port 11-13, which is adjacent the unloader mechanism for that cylinder, as will be seen below.

Referring to FIGURE 2, a portion of the three intake ports 11, 12, and 13, shown in FIGURE 1, are shown connected to a common intake or suction manifold 14. Each of the intake ports 11-13 has a conventional suction valve 15-17, respectively, which is urged towards closed position on its associated valve seat 18-20 by a valve spring 21-23, respectively. The remainder of the pump structure, such as the discharge valving, pump cylinders, pistons, etc. have been omitted from FIGURE 2 since they are entirely conventional.

Immediately below and coaxial with each of the suction valves 15-17 is a valve unloader device diagrammatically shown as including an air cylinder 24-26, an associated air piston 27-29 and an unloading stem 30-32, respectively. Each of the air pistons 27-29 and their associated unloading stems 30-32 is urged to an upper, valve open, position by an unloader spring 33-35 which has a high spring constant relative to the valve springs 21-23. As seen in the left-hand and center ports of FIG- URE 2, the unloading stems 30 and 31, when in upper position, push the suction valves 15 and 16, respectively, off of their seats 18 and 19 and hold these valves 15 and 16 open. As seen in the right-hand port, the unloading stem 32, when in its lower position with the unloader spring 35 compressed, releases the valve 17 so that it may seat upon its valve seat or be opened by a suction or intake stroke of its associated piston.

Connected to each of the air cylinders 24-26 above its associated air piston 27-29 are air supply lines 36-38 which are connected in spaced apart relationship to apertures in a fixed valve plate 39 of the timing control device shown in FIGURES 3 and 4.

Referring to FIGURE 4 the fixed valve plate 39 is secured to the outwardly facing rim 40 of a bell-shaped housing 41 by a plurality of bolts 42 which are threaded into tapped holes in the housing 41. A shaft 43, which is operably connected to and driven in synchronism with the crankshaft 44 of the reciprocating pump, as schematically shown in FIGURE 1, extends through a central opening in the housing 41 and is secured to a rotating valve plate 45 by a key 46 and a lock nut 47. One face 48 of the rotating valve plate 45 is adjacent the inner face of the fixed plate 39. These adjacent plate faces are separated by a packing or seal 49 which has a low coefficient of friction so that the rotating plate 45 can easily turn relative to the fixed plate 39 when the shaft 43 is turned by the crankshaft 44 of the reciprocating pump. The opposed faces of the valve plates 39 and 45 are maintained in close contact with the seal 49 by a spring 50 which is compressed between an internal flange 51 in the housing 41 and a collar 52 circumjacent the shaft 43. The collar 52 is pushed against a bearing 53 which is circumjacent a portion of the shaft 43 and whose inner face pushes against a hub 54 of the rotating valve plate 45.

Extending through the rotating valve plate 45 is a fluid aperture 55 which, when the valve plate 45 is turned, is positioned to come into alignment with the apertures in the fixed plate 39 which are connected to the air supply lines 36-38. As best seen in FIG. 3, when the rotating valve plate 45 is turned by its shaft 43, the fluid aperture 55 therein will successively become aligned with each of the apertures in the fixed plate 39. Thus, rotation of the rotating valve plate 45 will successively connect each of the supply lines 36-38 and its associated air cylinder 24-26 with the interior of the housing 41, as the rotating aperture 55 becomes aligned with the aperture associated with the air supply lines 36-38.

An air line 56 is connected between an aperture in the rear of the housing 41 and a three-way pneumatic valve generally designated by reference numeral 57 and schematically shown in FIG. 2. This valve 57, which may be solenoid operated by .means of appropriate electrical or pressure actuated controls, is connected to an air supply source by a line 58 and is also vented to atmosphere through a second line 59. When the valve 57 is in a first position, the air supply through line 58 is directly connected to the air line 56 and thus to the housing 41 and, when in a second position, the vent or exhaust line 59 is directly connected to the air line 56 and thus the housing 41. Thus, when the valve 57 is in its first position, the interior of the housing 41 adjacent the rear face of the rotating plate 45 is pressurized and when in the second position, this space is vented to atmosphere.

Operation of the pump unloader device is as follows. When the reciprocating pump is in normal operating condition, the control valve 57 is in its first position and thus the air space within the housing 41 has been pressurized. This air pressure has been transmitted through the rotating aperture 55 to the air supply lines 36-38 so that the air pistons 27-29 and the unloader stems 30-32 are all in their lower position. With the unloader stems 30-32 in their lower position, (corresponding to the position shown in the right-hand intake port in FIG. 2), the suction valves 15-17 are free to operate in the normal manner, being opened by the intake or suction stroke of their associated pistons and closed by the discharge stroke thereof.

When the operator wishes to unload the reciprocating pump, he causes the valve 57 to be moved to its second position in which the space within the housing 41 is vented to atmosphere through the lines 56 and 59. At this instant, the pressure within the air cylinders 24-26 and their associated supply lines 36-38 remains, due to the fact that this pressure cannot be released until the rotating aperture 55 in the rotating valve plate 45 becomes aligned one of the apertures in the fixed value plate 39 associated with the supply line 36-38. As previously stated, the angular relation between the crankshaft 44 and the position of the aperture 55 in the rotating valve plate 45 is such that the aperture 55 will not be in alignment with one of the apertures in the fixed valve plate 39 during a pressure or discharge stroke of the pump pistons. Stated conversely, the aperture 55 is aligned with one of the apertures in the fixed plate 39 only during the suction stroke of the associated pump piston. As the rotating plate 45 rotates, its aperture 55 becomes aligned with the aperture associated with air pressure line 38, as shown in FIG. 3 for instance, so that the pressure in line 38 and thus in the air cylinder 26 is released during the suction stroke of the piston associated therewith. Thus the suction valve 17 becomes unloaded during the suction stroke of its associated piston and, during the subsequent pressure stroke of that piston, the valve remains in open position due to the force of the unloader spring 35 so that no pressure can be developed in this cylinder. The fluid drawn in the cylinder from the intake or suction manifold 14 during the preceding intake or suction stroke is merely forced back into this manifold through the open valve 17. In like manner, the subsequent air cylinders 25 and 24 are unloaded during the suction strokes of their associated pistons.

When the operator moves the control valve 57 to its first position, so that the air pressure through the line 58 is in communication with the space within the housing 41, the suction valves 15-17 will not be loaded until the aperture 55 in the rotating valve plate 45 again becomes aligned with the corresponding aperture in the fixed plate 39. Thus the valves 15-17 can only be loaded during the suction or intake stroke of their associated piston. As previously explained, the loading and unloading of the valves 15-17 during the suction or intake stroke of their associated pistons prevent any damaging shock waves which would occur if the valves had been loaded or unloaded during the discharge stroke of their associated pistons. Also, the valves are loaded or unloaded in the predetermined sequence corresponding to the sequence of the suction strokes of their associated pistons, thus preventing the simultaneous loading or unloading of the entire reciprocating pump.

Referring to FIG. 3, the bolts 42 which attach the fixed valve plate 39 to the housing 41 extend through elongated slots 60 in the fixed valve plate 39. These slots 60 enable the angular position of the fixed plate 39 relative to the housing 41 to 'be adjusted in order to vary the timing of the loading or unloading of the suction valves -17 with respect to the suction stroke of their associated pistons. This timing adjustment could also be accomplished through means to vary the angular relationship between the chankshaft 44 and the shaft 43 which drives the rotating valve plate 45.

It is to be understood that the above described preferred embodiment may be used with both single and multiple cylinder reciprocating pumps and compressors and that the principle of unloading and loading the suction valves of such a pump or compressor only during the suction or intake strokes of their associated pistons may be accomplished in a variety of ways through use of various mechanisms. Other changes and modifications can be made from the specific details set forth herein without departing from the scope and spirit of the attached claims.

Iclaim:

1. A pump unloading device for a reciprocating pump having at least one cylinder and piston with a pressure actuated intake valve opened by movement of said piston during its suction stroke and closed by movement of said piston during its discharge stroke, said pump unloading device comprising, in combination, an unloading stem movable between a first position in which it holds said intake valve open and a second position away from said valve whereby said valve is free for normal operation, bias means urging said unloading stem in said first position and fluid pressure actuated override means eflective to overcome said bias means to move and hold said stem in said second position, and a control means for supplying fluid pressure to said pressure actuated override means in timed synchronism with said piston to load and unload said intake valve only during the suction stroke of said piston, said control means including a stationary valve plate having an air passage extending therethrough and operably connected to said pressure actuated override means, a driven valve plate adjacent said fixed plate, means connecting said driven plate with said piston for movement in timed synchronization therewith, a fluid passage positioned in said driven plate such that said fluid passages in said fixed and driven plates are in alignment only during the suction stroke said piston, a fluid pressure chamber in communication with the aperture in said driven plate and control means for selectively applying fluid pressure to and venting said fluid pressure chamber whereby, when said fluid pressure chamber is pressurized or vented by said selection means, said unloading stem will move only when said fluid passages in said driven and stationary plates are in alignment.

2. In a reciprocating pump having a plurality of cylinders with reciprocating pistons connected to a common crankshaft and having a predetermined suction and discharge stroke sequence and a pressure actuated fluid intake valve in each of said cylinders, each of which valves are opened by movement of its associated piston during its suction stroke and closed by movement of its piston during its discharge stroke and having a pump unloading device for holding said valves open during the respective discharge strokes of said pistons, said unloading device including an unloading stem for each of said valves movable between a first position in which it holds its associated valve open during the discharge stroke of its associated piston and a second position away from its associated valve whereby said valve is free to close during said discharge stroke of its associated piston, bias means for holding said unloading stems in their said first positions, and a fluid pressure actuated override means for overcoming said bias means and for moving and holding said unloading stems in their said second position, the improvement comprising a stationary valve plate having a plurality of equally spaced apart fluid passages extending therethrough with each of said fluid passages operably connected to a fluid pressure actuated override device associated with an unloading stem, a driven valve plate adjacent said fixed plate, means connecting said driven plate with said crankshaft for timed rotation in synchronism therewith, at least one fluid passage positioned in said driven plate such that a passage in said fixed plate will be in alignment with a passage in said driven plate only during the suction stroke of the piston associated with the unloading stem associated with each of said fixed passages in accordance with said predetermined suction stroke sequence, a fluid pressure chamber in communication with the apertures in said driven plate and selector means for selectively applying fluid pressure to and venting said fluid pressure chamber whereby, when said chamber is pressurized or vented by said selector means, said unloading stems will move only during the suction strokes of their associated pistons as said fluid passages in said driven and fixed valve plates become aligned.

3. The device of claim 2 wherein the angular position of said fixed plate with respect to said crankshaft may be adjusted to thereby vary the timing of the alignment of said air passages in said fixed and driven plates with respect to the timing of the suction strokes of said piston.

4. The device of claim 2 wherein said selector means is a fluid control valve operably connected between said fluid pressure chamber, a source of fluid pressure and a vent such that, when said control valve is in a first position, said pressure chamber is connected to said source of fluid pressure and when in a second position, said fluid chamber is connected to said vent.

References Cited UNITED STATES PATENTS 2,135,247 11/1938 Aikman 230223 2,227,260 12/ 1940 Holveck et a1 10340 3,039,393 6/1962 Yaindl 23028 ROBERT A. OLEARY, Primary Examiner. WILLIAM L. FREEH, Examiner. 

